In the field of computing, many scenarios may involve a content item, such as a news article, a factual description such as an encyclopedia, or a weblog post, which may involve one or more user updates, such as additions or changes of information or comments comprising a discussion of the content item. Such content items are often posted by a content item source, such as a webserver hosting a website comprising a set of content items, which may accept updates from users and associate them with the news article. In some scenarios, the user updates may be posted in a series that is organized in various ways (e.g., sequentially, by priority, or according to threads); in other scenarios, the user updates may comprise alterations of the body of the content item (e.g., an editable wiki page regarding a particular topic.)
A user who is interested in the topic of a content item may wish to follow the updates posted to the content item. In many such scenarios, the user may simply issue a series of requests to the content item source for the content item (such as a web page of a website), and may examine the content item for new material. In other scenarios, the user may be able to query the content item source for a list of updates, e.g., a real simple syndication (RSS) feed that presents a series of updates to the content item. In still other scenarios, the user may be able to request the content item source to notify the user upon receiving updates to a particular content item (such as a post in a web forum regarding a particular topic, for which the web forum software may be configured to send an email message to the user upon receiving an additional post in the topic.) However, some content item sources may not be configured to permit users to subscribe to updates, and users may have to visit and revisit many content item sources in order to remain informed about updates to particular content items of interest.